This invention relates to the field of remote terminals as used in wireline telephony, and, more specifically, to maintaining a translations database to effect call control in a remote terminal that routes telephone calls when communication between the remote terminal and its controlling switching system is lost.
Wireline telephone local exchange carriers use remote terminals (such as, but not limited to, subscriber loop carriers and digital loop carriers) to serve customer telephones that are too far from the nearest local switching office to provide acceptable service directly. A remote terminal is connected to a local switching office by one or more trunk groups, which provide voice paths and a control path between the local switching office and the remote terminal. The local switching office controls the remote terminal as if it were merely an extension of the switching office. There is no local controller or switch fabric in a remote terminal to save on cost, complexity and space. In this manner, subscribers that otherwise could not be served by conventional wireline telephony can be served by a remote terminal. Further, the telephone local exchange carrier does not have to build or buy expensive local switching offices or remote switching modules to serve only a few subscribers.
A problem in the art, however, is that control of the remote terminal is tightly coupled to the local switching office. Therefore, whenever the local switching office is out of service, or the umbilical trunk is cut, the remote terminal is out of service. When there is a problem the local switching office, the umbilical trunk, or both, there is no telephone service for the telephone customers served by the remote terminal, even though the problem may be many miles away. The remote terminal may be otherwise fully functional, but there is no control or switching fabric to perform the functions necessary to provide local service. While there are some suggestions in the art to add such switching capabilities to a remote terminal, none of these suggestions solve this problem without integrating equipment (such as processing units and switching fabrics) directly to the remote terminal. Such additional equipment amounts to replacing an inexpensive remote terminal with a relatively more expensive remote switching module (known in the art as a “forklift” replacement), which is what the service providers are trying to avoid.
Even given a system that can operate a remote terminal in stand-alone mode, the data used to route calls, kept in a database that is usually called a “translations database” must be kept synchronized with the data used by the controlling switching system for call routing. A translations database associates a line appearance or line ID with a telephone number. Further, the translations database associates emergency call routing information with the line ID for use when and emergency number, such as “9-1-1,” is called. In most situations, manually updating records for each and every change of telephone number or emergency call routing information is prohibitively expensive, time consuming and not necessarily performed as quickly as the updates are applied at the remote terminal's controlling central office.
Thus, there is no low cost method to operate a remote terminal in a stand-alone mode that can be implemented without a forklift replacement and/or a reconfiguration of the wireline infrastructure and there is no low cost method to maintain a translations database in synchronization with translation data in a controlling switch.